1. Field of the Invention
This invention relates to coupling devices and particularly to an apparatus for coupling external equipment to a seismic streamer cable.
2. Discussion of the Related Art
In the art of marine seismic exploration, it has been generally recognized that it is important to accurately determine the depth and location of substantially every point along the length of the streamer cable &:o provide more precise data. Since the early attempts to control the depth of the streamer cable, such as through the use of a single drogue assembly drawn behind the cable, or through the use of spaced weights and floats, considerable effort has been expended to control the cable depth at a desired point. Early approaches included placing a diving plane mechanism at spaced intervals along the length of the cable. The mechanism was mounted directly onto the cable by clamping two halves together with a series of nuts and bolts. These devices were time consuming and difficult to remove and replace. Similarly, external devices have been used to determine the areal location of points along the streamer cable with respect to the towing vessel. Attempts to accomplish this end have been made by attaching pinger devices externally to the cable much in the same manner as were the diving planes.
External cable connectors widely used in the industry have been manufactured by Laitram Corporation of New Orleans, Louisiana, and Syntron, Incorporated of Houston, Tex. These latching mechanisms for coupling devices external the seismic cable generally consist of collars mounted around the streamer cable at desired locations. Each collar may include two parts: a cylindrical inner race formed of two half-cylinder members which are semi-circular in cross-section coupled together by screws. The inner race receives an outer race or locking collar formed of two half-cylinder members which are also semi-circular in cross-section and coupled together by screws. The locking collar is free to rotate around the inner race. The locking collar has a detent consisting of a pair of locking slots at diametrically opposed positions. The locking slots are designed to slidably receive a screw set at a predetermined height on a shank or bracket coupled to the external device. The distance between the shank and the head of the screw is set so that the head of the screw will just be received by the locking collar and allowed to slide along an inner surface, leaving the shank substantially tight against the collar. The screw is slid to one end of the locking slot so as to enable a pin to be insert into the locking slot through the action of a cam or spring. Cams or levers have been provided to lower the pin and allow the shank to slide off the collar.
The cam operated pins in the mechanisms for coupling the external devices have the same problem as the diving planes. They require a tool to remove the shank from the collar. The spring operated pins have a disadvantage in that they provide a lever protruding from the side of the shank used to lower the pin which is exposed to ocean debris and may be inadvertently dislodged or lowered, allowing the shear stress inherent in such a system while under tow to be applied to the screw. This may result in failure of the latching mechanism and loss of the external device. Another disadvantage in the external lever or the spring-actuated latch is the turbulence generated do to their perpendicular orientation to the flow direction.
It is an object of this invention to provide a latching mechanism which does not require tools to attach or detach an external device to a streamer cable. It is another object of this invention to provide a latching mechanism which does not require tools to adjust the latching mechanism once the device has been attached and locked in place. It is yet another object of this invention to provide a latching mechanism which allows quick and efficient coupling and uncoupling of external devices. It is yet another object of this invention to provide a latching mechanism which is universally accepted by locking collars manufactured by others.